The infinity is an important concept which appears in most areas of the maths and physics. The maths is full of ideas that may seem counterintuitive (eg. "imag

The infinity is an important concept which appears in most areas of the maths and physics. The maths is full of ideas that may seem counterintuitive (eg. "imaginary unit" - the square root value of -1), but as long as they are precisely defined, they can be used in reasoning that gives practical results. And even if some math concepts can't be applied to anything practical yet, we never know what will be used to formulate another theory about the stock market behaviour or processes inside the black hole. Coming back to your question, here's an example: many math constants (pi, e) and functions (sin, cos) can be defined as infinite sums (series). They converge, getting closer and closer to the limit, but they never achieve it. Using these series it's possible to calculate (in a calculator, Excel, Quake or CAD) values of these functions with any required precision.